6.1.3 File Descriptor Operations

















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6.1.3 File Descriptor Operations



These functions operate on I/O streams referred to
using file descriptors.


close (fd)

Close file descriptor fd.
Availability: Macintosh, Unix, Windows.


Note: this function is intended for low-level I/O and must be applied
to a file descriptor as returned by open() or
pipe(). To close a ``file object'' returned by the
built-in function open() or by popen() or
fdopen(), use its close() method.



dup (fd)

Return a duplicate of file descriptor fd.
Availability: Macintosh, Unix, Windows.



dup2 (fd, fd2)

Duplicate file descriptor fd to fd2, closing the latter
first if necessary.
Availability: Unix, Windows.



fpathconf (fd, name)

Return system configuration information relevant to an open file.
name specifies the configuration value to retrieve; it may be a
string which is the name of a defined system value; these names are
specified in a number of standards (POSIX.1, Unix95, Unix98, and
others). Some platforms define additional names as well. The names
known to the host operating system are given in the
pathconf_names dictionary. For configuration variables not
included in that mapping, passing an integer for name is also
accepted.
Availability: Unix.


If name is a string and is not known, ValueError is
raised. If a specific value for name is not supported by the
host system, even if it is included in pathconf_names, an
OSError is raised with errno.EINVAL for the
error number.



fstat (fd)

Return status for file descriptor fd, like stat().
Availability: Unix, Windows.



fstatvfs (fd)

Return information about the filesystem containing the file associated
with file descriptor fd, like statvfs().
Availability: Unix.



ftruncate (fd, length)

Truncate the file corresponding to file descriptor fd,
so that it is at most length bytes in size.
Availability: Unix.



isatty (fd)

Return 1 if the file descriptor fd is open and connected to a
tty(-like) device, else 0.
Availability: Unix



lseek (fd, pos, how)

Set the current position of file descriptor fd to position
pos, modified by how: 0 to set the position
relative to the beginning of the file; 1 to set it relative to
the current position; 2 to set it relative to the end of the
file.
Availability: Macintosh, Unix, Windows.



open (file, flags[, mode])

Open the file file and set various flags according to
flags and possibly its mode according to mode.
The default mode is 0777 (octal), and the current umask
value is first masked out. Return the file descriptor for the newly
opened file.
Availability: Macintosh, Unix, Windows.


For a description of the flag and mode values, see the C run-time
documentation; flag constants (like O_RDONLY and
O_WRONLY) are defined in this module too (see below).


Note: this function is intended for low-level I/O. For normal usage,
use the built-in function open(), which returns a ``file
object'' with read() and write() methods (and many
more).



openpty ()

Open a new pseudo-terminal pair. Return a pair of file descriptors
(master, slave) for the pty and the tty,
respectively. For a (slightly) more portable approach, use the
pty module.
Availability: Some flavors of Unix



pipe ()

Create a pipe. Return a pair of file descriptors (r,
w) usable for reading and writing, respectively.
Availability: Unix, Windows.



read (fd, n)

Read at most n bytes from file descriptor fd.
Return a string containing the bytes read.
Availability: Macintosh, Unix, Windows.


Note: this function is intended for low-level I/O and must be applied
to a file descriptor as returned by open() or
pipe(). To read a ``file object'' returned by the
built-in function open() or by popen() or
fdopen(), or sys.stdin, use its
read() or readline() methods.



tcgetpgrp (fd)

Return the process group associated with the terminal given by
fd (an open file descriptor as returned by open()).
Availability: Unix.



tcsetpgrp (fd, pg)

Set the process group associated with the terminal given by
fd (an open file descriptor as returned by open())
to pg.
Availability: Unix.



ttyname (fd)

Return a string which specifies the terminal device associated with
file-descriptor fd. If fd is not associated with a terminal
device, an exception is raised.
Availability: Unix.



write (fd, str)

Write the string str to file descriptor fd.
Return the number of bytes actually written.
Availability: Macintosh, Unix, Windows.


Note: this function is intended for low-level I/O and must be applied
to a file descriptor as returned by open() or
pipe(). To write a ``file object'' returned by the
built-in function open() or by popen() or
fdopen(), or sys.stdout or sys.stderr, use
its write() method.



The following data items are available for use in constructing the
flags parameter to the open() function.


O_RDONLY

O_WRONLY
O_RDWR
O_NDELAY
O_NONBLOCK
O_APPEND
O_DSYNC
O_RSYNC
O_SYNC
O_NOCTTY
O_CREAT
O_EXCL
O_TRUNC
Options for the flag argument to the open() function.
These can be bit-wise OR'd together.
Availability: Macintosh, Unix, Windows.



O_BINARY

Option for the flag argument to the open() function.
This can be bit-wise OR'd together with those listed above.
Availability: Macintosh, Windows.









Python Library Reference




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